Probing fretting performance of DLC and MoS2 films under fluid lubrication

Transition from onefold to synergistic lubrication for solving fretting wear and fatigue problems is of great practical significance, because fluids can regulate fretting regime for minimizing wear, solid films can restrain nucleation and formation of crack. Here synergistic lubrication coatings were prepared using diamond-like carbon (DLC) and molybdenum disulfide (MoS2) films as anti-wear/fatigue layer, and high-performance lubricants (including silicone oil, ionic liquids, multialkylated cyclopentanes and perfluoropolyethers (PFPE)) as flowable lubrication layer. Their fretting performance was evaluated in detail and fretting mechanism was revealed by surface/interface analysis techniques. Results determine the synergistic lubrication coatings with good anti-wear and anti-fatigue abilities, deriving from the synergy of improved yield strength and shear strength, transfer layer and boundary film. Moreover, the fretting regime is pointedly regulated by solid films with different composition and performance, for example, DLC-based lubrication coatings under applied load of 22 N correspond to slip regime, so do as the MoS2-based coatings under 4 N, and PFPE-lubricated MoS2 films display better anti-wear ability than others, while DLC under PFPE lubrication reverses. The choice of optimal scheme depends on the working condition and lubrication state for achieving the requirements of high reliability, high precision, high efficiency, and long lifetime.